Foreign Object Deposits (FOD), such as debris from a burst tyre of an aircraft, are objects which should at all costs, not be allowed to lie on an airport runway. FOD present a potentially serious danger to the safety of aircraft during take-off and landing. For example, the Supersonic Air France Concorde Flight AF4590 crash in Paris on 25 Jul. 2000 was due to an FOD: a 16-inch piece of metal present on the runway surface. Such objects may come from passengers, airport staff, machinery or even wildlife.
Notwithstanding the potential damage to an aircraft, if a jet engine is damaged by the ingestion of FOD into the engine (i.e., during taxiing), the maintenance costs can easily exceed USD1 million. Even a relatively small FOD (i.e. less than 50 mm in diameter) may cause harm to engines and fuselages of aircraft.
Most airports have implemented runway maintenance programs for removing FOD according to international aviation standards (e.g., International Civil Aviation Organization Annex 14 regulations). The Federal Aviation Authority in the US recommends a minimum of two inspections and one runway sweep daily. Currently, a typical sweep involves a runway being swept once daily by two runway sweeper vehicles operating at 25˜35 km/h. Each runway sweeper vehicle has a driver and an inspector onboard. Sweeping is performed by a magnetic bumper in combination with a central brush and suction.
The typical manual sweeping practice is repetitive in nature because the manual sweeping practice relies only on human visual inspection together with a sweeper vehicle for sweeping a found FOD, which is time consuming as well as expensive. For example, it takes 1.5 hours and two sweepers with one human inspector on each sweeper to scrutinise a 50 meter wide 4 km long runway. Inevitably, poor lighting, weather changes and human fatigue compromise the effectiveness of sweeping. Furthermore, known sweeping processes lack verification of sweeping effectiveness because no immediate post-sweeping inspection takes place. If a heavy, non-ferrous foreign object which cannot be picked up by the magnetic bumper or is too heavy to be sucked up by a vacuum (e.g., an aluminium part) is left on the runway after sweeping, it may pose a grave danger to aircraft using the runway. Hence, automatic systems have been proposed for monitoring, alerting or picking up FOD on airport runways.
One known system proposes distributing a large number of automated robotic vehicles besides each runway to monitor and pick up FOD on a continuous basis. These robotic vehicles are less than 900 mm in height and each of them is constrained to work within a predetermined area by a network of rails. There are some major problems associated with this robotic system. Firstly, the system requires a large number of robotic vehicles to be positioned beside each runway. Secondly, data transmission and processing between the vehicles and the airport control tower further overloads airport staff and equipment. Thirdly, the system requires the robots to be located adjacent to the runway, which is generally undesirable as the runway and its immediate surroundings should be kept clear. Fourthly, the cost for implementing and maintaining the large number of robotic vehicles for an airport is expected to be prohibitive.
There is a need to provide a detection system or vehicle that overcomes, or at least ameliorates, one or more of the disadvantages described above.